Search for Outer Massive Bodies around Transiting Planetary Systems: Candidates of Faint Stellar Companions around HAT-P-7

TL;DR

This study used direct imaging to identify potential faint stellar companions around HAT-P-7, exploring their possible influence on the orbital dynamics of its transiting planet, HAT-P-7b.

Contribution

First direct imaging search for faint stellar companions around HAT-P-7, providing insights into the system's dynamical history and potential mechanisms for orbital tilt.

Findings

Detected two candidate faint stellar companions.

Suggests Kozai migration is less likely due to the third body presence.

Indicates planet-planet scattering as a plausible orbital evolution process.

Abstract

We present results of direct imaging observations for HAT-P-7 taken with the Subaru HiCIAO and the Calar Alto AstraLux. Since the close-in transiting planet HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as giant planets, brown dwarfs, or a binary star are expected to exist in the outer region of this system. We show that there are indeed two candidates for distant faint stellar companions around HAT-P-7. We discuss possible roles played by such companions on the orbital evolution of HAT-P-7b. We conclude that as there is a third body in the system as reported by Winn et al. (2009, ApJL, 763, L99), the Kozai migration is less likely while planet-planet scattering is possible.